Process of distilling mineral oil



April 2, 1929. A. E. PEw, JR 1,707,448 f PROCESS OF DISTILLNG MINERALOIL Filed Dec. 22, 1926 /4 fra/iwf Vs.

Patented Apr.l 2, 1929.

uNrrEu STATES PATENT OFFICE.

" ARTHUR E. PEW`,.JR., oF BRYN MAWR, PENNSYLVANIA, AssIGNoR '.ro sUN on.com- PANY, or PHILADELPHIA, PENNSYLVANIA, A CORPORATION oF NEW JERSEY.

PROCESS 0F DISTIIIJIITNG MINBAL OIL.

Application illed December 22, 1926. Serial No. 156,289.

The use of steam in stills for distilling hydrocarbon mixtures, andparticularly mineral oil, for the purpose of agitation and consequentturbulence, with lowered vapor tension due to the presence of the steam,has long been known andpracticed, both in stills operating atsubstantially atmospheric pressure and inLstills operating under vacuum.,There are many plants today operating at quite high vacuums which usesteam as a means for agitating the oil in the stills, thus preventingaccumulation of dirt on the bottom sheets and incidentally lowering theboiling point of the oils by lowering the vapor tension. The turbulence.

obtained in a still by the use of steam materially increases thecapacity of the still, since the heat transfer is much greater than whenthe still isrun dry,

However, it lias'long been thought that the use of steam" necessarilyresults in the overhead distillate 4being of inferior color as comparedwith such oils obtained in high vacuum distillation without the use ofsteam. In the course of my experimental work,l I distilled Various oilsunder vacuums ranging from 28 to 29 inches. In order to lower theboiling points of'the oil under thisvacuum and in order to get goodagitations to prem vent burning and local overheating, steam wasadmitted beneath the surface of the oil.

, The steam was generated in a still under a vacuum slightly lower thanthe vacuum in the stilL This was necessary in -order to generate enoughpressure in the steam still vto push steam through the oil in the oilstill. The distillates thus obtained were of better quality than wereobtained from the distillation of the same oil under a vacuum of from 3to 4 mm. without the presence of steam. The reasons for this result Ibelieve to be as follows:

The volume of one poundofsteam at atmospheric pressure is 26.79 cubicfeet. The volume of one pound of steam at 28.5 inches of vacuum is 469cubic feet. By the process of generating steam under vacuum, the steamhas fully expanded, or substantially so, when it Venters the oil in thestill.. This makes it necessary to use less steam than would be requiredin a still operating at atmospheric pressure with steam at ordinarypressure, the agitating effect of steam being largely volumetric. Steamcould be admitted to the still from a line operating at. any pressure,but the instant the steam leaves the nozzles and is injected into theoil in the stills when such still is operating under high', vacuum, itis subject to the absolute pressure which is on the still, namely, avery high vacuum. The steam expands instantaneously according to thedifference of pressure at the injector and that on the still. Thisrapidl expansion has a tendency to cause entrainment as the steam passesupward through the oil. This entrainment would have a bad effect on thecolor of the distillates. However, when steam is generated undersubstantially the same vacuum as is applied to the oil still, the steamis a1- relady expanded at the instant it hits the o1 As a matter ofoperatingeconomy, it is quite eiiicient to use steam generated undervacuum, since on all vacuum plants it is necessary to have a vacuum pumpor steam ejector, and the exhaust steam from such apparatus can be usedthrough coils in the boiler for the generation of steam under vacuum.For example,v the boilingv point of water at 27.3 inches ot' vacuum isonly 110 F.,v whereas the temperature of steam at two pounds gaugepressure is 218 F., giving a difference in temperature of 108, which isample for the transfer of heat from steam to water economically.

However, the reasons which have just been outlined do not fully explainthe great benefit to be derived from the present process. Ordinaryboiler feed Water contains from 1% to 4% ofl airby Volume. Air is 78%nitrogen by volume and approximately 21% oxygen, the balance vbeinargon. ien such water is distilled an the steam used in any oil still,the air enters the hot oil along with the steam in more than suflicientquantities to cause substantial oxidation of the distillates. Evidenceof this is comparatively poor color and noticeable acidity.

The fact that air in water causes corrosion is well known in boilerpractice, corrosion being the result of oxidation. The last decribedoperation ai'ords definite proof that the oxygen in the air does act asan oxidiz- #ing agent.

er methods. For example, advantage cany be taken of known laws ofpartial pressures by bubbling exhaust steam through the water in suchquantities that the resultant tot-al pressure would be very great inproportion to the partial pressure due to the air in the water. Byremoving air from water by any suitable method, and then converting suchair-free water into steam, and injectin the steam into a body of oilbeing ldistille under vacuum, distillates are obtained that aresatisfactory as to color as well as to general quality. l

This last described process'v constitutes, broadly, my invention,although the process embodies other important features, which canbest beunderstood by an explanation of the apparatus shown in the accompanyingdrawing. Although the process is not de-4 pendent for its execution onany particular apparatus, that herein illustrated and described has beenfound eiiicient.

The ligure is a diagrammatic view of apparatus wherein my invention maybe practice Water is pumped through line 8, at a temperature of aproximately 120 F., into an evaporator tan 10. Here the water flows at hih velocities and in turn films over incline plates 9. Tank 10`ismaintained under a vacuum of (say) 28 inches. At 28 inches of vacuum,the boiling point of water is 100 F. and at 26.4 inches ofvacuum it is,120 F. Hence, due to the vacuum in the Vthrough line 4 to brinev cooler2. Cooled brine 1s pumped throu h tubes in this cooler, therebyextracting t e heat from .the water vapor and air, and thus condensingthe y water. The air is sucked to a vacuum pump Water substantially freeof air then ilowsf.

from the kbottom 'of evaporator 10 into line lthe feed Y 11 and lthenceinto boiler12. Difference in elevation between vaporizer 10 andfboile'r12',` 4 ,v l or a seal on line 11, compensatesrfor the difference inpressure between 'boiler 12 and i vaporizer 10.- On the assumption'fthatstill 19 operates at 28.9 inches of vacuiii'nand.has1V 4 feet of oil inthe still, thisjhead' of oilis equivalent to a-pressure of about min. Qwhich is equivalent to 3 inches'of mercury.

Hence, in order to get the steam from boiler 12 into still 19 there mustbe a vacuumin boiler 12 of 25.9 inches or a `littleffless,"de-

pending on line friction, say 25175,inches. .I Under this vacuum, waterboils at"130."F.

Summarizing: vaporizer 10 is maintainedat 28 inches of vacuum, waterentering at `120" F. and leaving at 100 F.; boiler 12 is malin tained at25.5 inches of vacuum andthe water. is heated therein to 130 F.; `still19 is maintained at 28.9 linches of vacuum and containsl oil having adepth of fourfeet Stem is admitted through pipe 13Y tothe` I steam coilin the boiler. This steam may be the exhaust from the vacuum pump `The95 condensed steam is run out as water through pipe 14. A drain 15 isappended 'tothe'V boiler. l

Still 19 is charged through line 18 and may be drained through line 17.The 'still may be run continuously or intermittently. Steam from boiler12 passes through'line 16 and into distributor pipes 20, whence it flowsthrough the main body of oil in still 19. i t

`Oil vapors and steam leave still` 'y19-.1651

through pipe 21 and pass into tower `22.

This tower is surroundedv by an insulated air f. Jacket 23, air-beingadmitted through :fines I 24 and passing upwards through-"passages- 23and past damper 31 into the atmosphere.

The described passage of air cools the mix-,z ture yof oil vapors .andsteam,toanyfdesired In 'the illustrated apparatusjihe degree.

vapors',v are cooled suiilcientlyto'gcondense the lubricating'oilfractons,'which pass-out through line 25 and condenser 26 v'int'olre-lceiving tank .27, and lthrough lin`eff-z29 yto pump and storage. Avacuum` is maintained on this tank through lines 28 and 40 to afp vacuumpump (not shown). .Y

The uncondensed steam and lighter 'oils pass out thetop of tower 22 Iline 32'to separator 3ft- 35. v .v

This separator is constructedwith 'an air 22. A mixture of oil vaporsand 'steam passes downward through the annular chamber 34 and thence uward through the inner or central cham r- 35. In traversing vby means il jacket 33 similar -to the-air jacket int-awel'.

1o harometric -injection condenser 46.

these chambers the oil vapors are condensed, transferring their heat tothe air in jacket 33. Thecondensed oil runs out through line 36, cooler37 and line 38 to tank 41, and thence through line 42 to storage. Avacuum is maintained by means of lines 39 and 40 to the last mentionedvacuum pump. y

The steam, still uncondensed, passes out the top of chamber 35 throughline 45 to a Here waterlis injected through line 47 into condenser 46,which condenses the steam, the condensate and the injected water passingdownstand pipe 48 to a barometric seal 55, which has an overflovvthro'ghline 53, and

a drain 54. Watervapors and non-oondenfv sable still gases pass into anejector or a wet orl dry vacuum pump 49.r If this is an ejec," tor,steam is admitted through line "56 and exhausted through line 50. l v jThere are substantial advantages in ada t inv the invention to otherprocesses of isti ing oil, such asthose disclosed in the applicationsfiled by Pew and Thomas March 5,

1925, Serial N o. 13,040, and by me May 29,v

1926,A Serial No'. 112,485; but the describedv application of theinvention to a simple and Well known type of oil still (19) .disclosesthe invention in a simple form. It will be understood, however,'that theprocess is applicable vto any known method of vacuum distillation. 1

Having now fully described my invention,

what I claim and desire to protect lby Let? ters Patent is:

1; The process of vaporizing oilk which comprises removing air fromwater, generating ste-am from` such water and mixing such steam withythe oil. .v

2. The process of 'vaporizing oil which comprises removing air fromwater, vgen. erati'ng steam from such water under a partial vaCuUm,mixingsuch steam with the oil, and maintaining a higher vacuum on theoil during its vaporization.v 3. The process of Yvaporizing oil whichcomprises owing Water in shallow streams over extended surfaceswhile'subjecting it to a high vacuum and thereby deaerating the water,generating steaml from such Water under a substantial vacuum, mixingsaid steam with the oil, and maintaining the'oil under a higher vacuumthan that under which the steam is generated.r f i 4. The process ofdistilling oil which comprises flowingv Water in a 'shallow stream overextended surfaces' while subjecting it to a high vacuum: andA therebyremoving most of the'- air from the water, heating. the des aeratedwater-to convert itinto steam substantially devoid ofI air, injectingsaid steam into the oil while ymaintaining the oil under vacuum,andcondensing the oil vapors thereby enabling vthe production of ,anv oidistillate substantially free from the decomseparating them fromuncondensed `by heat exchangeof the oil vapors and steam positionproducts produced by high temperature and substantially free from theoxidation products produced by the contact of the oil with oxygen.l

y 5. The process 'of 'distilling oil which comprises removing air fromWater, generating steam from such-water, mixing such steam With the oil,and by'heat exchange with a4 exchange of Atheoil vapors and steam With'a current of air, and passing uncondensed steam-v and lighter-'oilvapors into heat exchange with a current of air and thereby condensingsuch lighter oil vapors and separatl ing them from nncondensed steam.

r, 7. The process of distilling oil which comprises removing air fromwater, gen-- erating steam from such water, mixingsuch.

steamy-with the oil, condensing oil vapors and steam with a current ofair, and condensing the steam fromn which the condensed yoil hasseparated. v

8. The process of distilling oil to produce distillates of high qualityand good color notwithstanding the injection of steam into theoi1,'which comprises substantially avoid` ing oxidation of thedistillates'by mixing with the oil steam from which a greatlyvpredominant proportion of its content of airv has been removed.

9. The process of distilling oil which comprises maintaining the oilunder a low subatmospheric ressurev and mixing .with the oil steam un era sub-atmospheric pressure suihciently higher than the pressure on theoil to enable the steam to be forced into the oil and sufficiently lowto minimize; thev volumetric expansion of the steam when admitted to theoil and the resultantl entrainrl ment as the steam travels through theoil.

removed and forcing the deaerated' steam.

.into the oil under a sub-atmosphericpressureyl vabove that to which theoil `is sub'ected but l suiciently low to minimize the e ect of its fexpansion and the resultant entrainment ,as

the steam travels through the oil.

1 1. ';[`11e process of vaporizing oil which comprises removing air fromwater, generatingfsteam from such water, maintaining'y von. 'the 011 alow subfatxnosphericv absolute pressure'lower than the absolute pressureunder which the steam Wes generated, end Inxing' the steam, as it isgenerated, with the o1 12. rThe process' of veporizing oil whichcomprises removing air from Water by Howin the Water over yen extendedsurface while su jectng it to e, 10W sub-atmospheric pressure, vgenerating steam from said Water 1Q under e, higher sub-atmosphericpressure,

merma mixing such steam with the oii, and mainmining on the oil esub-atmospheric' absolute pressure lower than the absolute pressureunder which the steam was generated.

In testimony of which invention, I have hereunto set my henci, atPhiladelphia, Pennsylvania, on this 15th dey of Becember, 1926.

ARTHUR n. PEW, en.

